John Key and Andrew Little traded verbal blows in Parliament today over the Trans Pacific Partnership.
Mr Little objected to other countries having a say on New Zealand laws that could affect them but Mr Key said it was no different to Mr Little wanting a say on Australian laws that affected New Zealanders.
The Labour leader travelled to Canberra last November to make a submission to a select committee on a law that changed the immigration status of New Zealanders who have been sentenced to a year or more in an Australian prison.
"So he has got a massive problem with everybody else doing it except himself," Mr Key said.
"Anyone is free to come and put in a submission about New Zealand but this Parliament determines its law, and this Parliament on its own."